Technical Abstract:
Rice blast and sheath blight are major fungal diseases of cultivated rice (Oryza sativa L. ) that limit Arkansas rough rice yields and market potential. Resistance to these diseases has been found in rice wild relatives (Oryza spp.) A collection of these wild relatives originating from outside the United States was evaluated for resistance to blast races found in Arkansas. DNA (simple sequence repeat, SSR) markers were used to 1) determine the genetic background of these Oryza spp. accessions, 2) identify SSR markers associated with blast and sheath blight resistance in these Oryza spp. accessions, and 3) compare marker associations found in the Oryza spp. with those differentiated in the U.S. and international O. sativa accessions to identify new chromosomal regions associated with disease resistance. The Oryza spp. accessions included in this study were determined to have eight different genetic backgrounds or ancestries based on SSR marker analysis. Three O. nivara accessions containing the most blast resistance genes all share the same background, identified as K3 in this study. Sixteen chromosomal regions with associations between blast resistance (R-) genes and an SSR marker were identified. At least six associations were in chromosomal regions previously not reported to contain blast R-genes. These chromosomal regions will be characterized further in the mapping populations developed from crosses with U.S. rice cultivars. Blast resistant germplasm lines developed from these populations will be made available to U.S. rice breeders.